Use of fine grain emulsion with coarse grain emulsion to reduce image spread

ABSTRACT

PHOTOGRAPHIC ELEMENTS HAVING COATED ON ONE SIDE OF A SUPPORT: (1) AN ANTIHALATION LAYER; (2) A FINE GRAIN SILVER HALIDE EMULSION LAYER; AND (3) A COARSE GRAIN SILVER HALIDE EMULSION IMAGE RECORDING LAYER WHICH PREFERABLY CONTAINS A PHOTOGRAPHIC COLOR-FORMER, EXHIBIT LOW IMAGE SPREAD.

United States Patent 3,591,382 USE OF FINE GRAIN EMULSION WITH COARSE GRAIN EMULSION TO REDUCE IMAGE SPREAD Allan G. Millikan, Webster, N.Y., assignor to Eastman Kodak Company, Rochester, NY.

No Drawing. Continuation-impart of application Ser. No. 648,237, June 23, 1967. This application May 15, 1968, Ser. No. 729,432

Int. Cl. G03c 1/76 U.S. CI. 96-68 9 Claims ABSTRACT OF THE DISCLOSURE Photographic elements having coated on one side of a support: (1) an antihalation layer; (2) a fine grain silver halide emulsion layer; and (3) a coarse grain silver halide emulsion image recording layer which preferably contains a photographic color-former, exhibit low image spread.

This application in a continuation-in-part of our copending Millikan application Ser. No. 648,237, filed June 23, 1967, now abandoned.

This invention relates to photographic materials and methods, and more particularly to photographic materials and methods for providing images having low image spread.

When conventional films are used to record images of grossly different intensities which are geometrically close together in the image plane, the over-exposed image obscures the image of lower intensity. This problem can be illustrated in photographing certain stars, such as the binary star Sirius A and Sirius B. Sirius B has a stellar magnitude (m.) of 8.4 and Sirius A has a stellar magnitude of -1.6 m., a difference of 10 m. In other words, Sirius A is ten thousand times as bright as Sirius B. Attempts to record images of these two stars on conventional film is unsatisfactory since the image of Sirius A spreads and obscures the image of Sirius B.

It has been proposed, for example in Russell British Pat. 1,000,001 (complete specification published Aug. 4, 1965) to modify effective speed and contrast by coating an optically sensitized silver halide emulsion over a nonoptic-ally sensitized silver halide emulsion layer. While such films are useful for the purposes intended, they do not provide sufficient reduction of image spread to be useful in various applications, such as stellar photography, which require recording the images of grossly different intensities which are located geometrically close together in the image plane.

One object of this invention is to provide novel photographic elements.

Another object of this invention is to provide novel photographic elements which exhibit low image spread.

A further object of this invention is to provide a novel method for preparing photographic images which exhibit low image spread.

These and other objects of this invention will be apparent from the disclosure herein and the appended claims.

In accordance with one embodiment of this invention, a photographic element is provided comprising a support having coated on one side thereof, in the order given; an antihalation layer; a first emulsion layer comprising fine silver halide grains dispersed in the photographic binder; and, an image recording layer comprising light-sensitive silver halide grains, which are relatively coarse, dispersed in a photographic binder.

In another preferred embodiment of this invention, a photographic element is provided as described above except that a photographic color former is incorporated in the image recording layer.

In still another embodiment of this invention, a photographic element is provided as described above wherein the first emulsion layer, which comprises fine silver halide grains, contains filter material which absorbs radiation longer than blue radiation (up to about 500 nm.) such as green and red radiation. Photographic elements in accordance with this embodiment of the invention exhibit an additional reduction in image spread when the image recording layer is sensitive to radiation longer than blue radiation (about 400 nm.) and when exposure is made with radiation longer than about 500 nm., such as white light. The silver halide grains of the image-recording layer can be spectrally sensitized with any of the dyes suggested in the prior art for that purpose. Panchromatically sensitized silver halide grains are especially useful when exposure is made with white light.

In a further embodiment of this invention, a method is provided for recording images of grossly different intensities in close geometric proximity in the image plane by exposing said images on a photographic element of type described above, developing the photographic image and removing undeveloped silver halide. When the photographic element used contains a color former, a suitable photographic color developer is employed, such as a primary aromatic amino color developing agent, e.g., a pphenylenediarnine color developer.

In accordance with the invention, a first emulsion layer is employed which is about 10 to about 40 microns in thickness, and comprises silver halide grains having an average diameter of from about .1 to about 1 micron. It is a relatively fine grained emulsion. This layer appears to function as a light diffusing layer. During processing, the silver halide in this layer is removed in any suitable manner such as with a silver halide solvent, e.g., sodium thiosulfate. The layer should be free from any light diffusing material, such as starch, which cannot be readily removed.

The image recording layer in accordance with the invention comprises relatively coarse silver halide grains, preferably having an average grain size within the range of from about 1 to about 4 microns. The image recording silver halide emulsion layer is advantageously from about 1 to about 10 microns in thickness.

The silver halides employed in either of the emulsion layers of the invention can be any suitable silver halide, such as silver chloride, silver bromide and silver iodide, or mixed silver halides such as silver chlorobromide, silver bromoiodide and silver chlorobromoiodide. In these layers, the binder for the silver halide can be any of the usual photographic binders. Gelatin is a highly useful and preferred binder. Other binders which can be employed herein with good results are described and referred to in column 13 of Beavers U.S. Pat. 3,039,873 issued June 19, 1962. In addition to such binders, also useful are binders of the type disclosed in U.S. Pats. 3,142,568; 3,193,386; 3,062,674 and 3,220,844, including the water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

In the preferred embodiments of this invention, a color former is incorporated in the image recording layer. It has been found that photographic element of this type produce the greatest reduction in image spread.

As used herein, the term color former includes any of those compounds which react or couple with the oxidation products of primary aromatic amino developing agents to form a dye. Preferably, they are non-diffusible in photographic silver halide emulsions. Typical useful color formers include phenolic, 5-pyrazolone, heterocyclic and open-chain ketamethylene compounds. A number of typical specific color formers which can be employed in the photographic elements of this invention are described in the literature. Any of the color formers described in Graham et al. U.S. Pat. 3,046,129, issued July 24, 1962, col. 15, line 44 through col. 18, line 51 can be used herein. The color formers can be incorporated in the emulsion in any convenient manner, such as by the procedures described and referred to in US. Pats. 2,322,027 and 2,801,171.

This invention will be further illustrated and better understood by reference to the following layer arrangements:

Layer 3Image recording layer Layer 2First emulsion layer Layer 1Antihalation layer Support In accordance with the invention, an antihalation layer is employed which is coated on the same side of the support as the emulsion layers. It is desirable to coat the antihalation layer on the same side of the support as the emulsion layers to obtain the desired reduction in image spread. Any suitable antihalation material can be em ployed. For example, dyes can be used, preferably those which absorb the longest wavelengths of radiation to which the emulsion is sensitive. The dyes should be decolorizable during processing, e.g., in sulfite solution. A large number of dyes which can be used in antihalation layers are described in Jones et al. US. Pat. 3,282,699, issued Nov. 1, 1966. Also useful as antihalation layers are colloidal silver layers such as neutral (gray) colloidal silver dispersed in a suitable colloid such as gelatin. Bleachable dyes are especially useful.

When the elements of this invention are exposed to blue radiation, low image spread is exhibited even when the first emulsion layer comprising fine silver halide grains does not contain any filter material. When exposure is made to radiation of longer wavelengths than blue radiation (about 400 to 500 nm.), such as to green (about 500-600 nm.) or red (about 600-700 nm.) radiation, or to white radiation (about 400 to 700 nm.), it is desirable to incorporate in the fine grain emulsion layer filter material which absorbs radiation longer than blue radiation. Any suitable filter material, such as pigment, a dye or combination of dyes can be used, such as the dyes of Brooker et al. in US. Pat. 2,917,516, issued Dec. 15, 1955, or those of Rosenolf U.S. Pat. 3,177,210, issued Apr. 6, 1965.

The image forming emulsion layer can contain any of the chemical sensitizers, spectral sensitizers, speed increasing compounds, plasticizers etc. referred to in Beaver US. Pat. 3,039,873. The non-image forming emulsions can be desensitized, if desired. The layers of the invention can be coated on any suitable support, such as glass, paper, polyolefin coated paper, film bases such as polyester, polycarbonate and cellulose acetate film bases. Preferably, the support is a film base which is laminated to glass.

The present invention will be further illustrated by the following examples.

Example 1 shows a preferred photographic element in accordance with the invention.

EXAMPLE 1 On a cellulose acetate film support there is coated an antihalation layer of the type described in Example 2 of Jones et al. U.S. Pat. 3,282,699. Over the antihalation layer is coated a first silver bromoidide gelatin emulsion (5 mole percent of the halide being iodide) and having a grain size of approximately 0.25 micron, at a coverage of 500 mg. silver per square foot. The layer has a thickness of about to 12 microns. An image recording layer is then coated over the first emulsion layer. The image recording layer consists of a gelatin silver bromoiodide emulsion (six mole percent of the halide being iodide) and having an average grain size of 2.0 to 2.5 microns. This emulsion layer is coated at the rate of mg. silver per square foot. The image recording layer also contains a dispersion in tri-o-cresyl phosphate of a pyrazolone coupler, e.g., couplers No. 7 etc., of Fierke et al. US. Pat. 2,801,171 (col. 2) at a concentration of 65 mg. per square foot coupler. The image recording layer is approximately 4 microns in thickness. A clear gelatin protective overcoating layer is coated over the image recording layer at the rate of 82 mg. of gelatin per square foot. The coated cellulose acetate film support is then laminated to glass. Two circular images, each 240 microns in diameter, are contact printed, one with an exposure sufficient to give maximum density (IX), and the other with an exposure 20,000 times greater (20,000X). The exposed element is then developed with a primary aromatic amino color developing agent, forming a metallic silver image. Oxidized color developer reacts with the pyrazolone coupler in the emulsion to form a magenta dye image. The silver and undeveloped silver halide are then removed from the emulsion layers. The color development process is described in detail by Millikan in Example 1 of Canadian Pat. 726,137 issued Jan. 18, 1966. The size of the dye images formed at the different exposure levels are measured. Low image spread is obtained, as shown in Table I, below.

Examples 2 and 3 illustrate the undesirably high amount of image spread which is obtained with photographic elements of the prior art.

EXAMPLE 2 A high speed photosensitive silver bromoiodide emulsion is coated on a glass support, and is exposed in the same manner as that described in Example 1. The exposed element is then processed at room temperature for four minutes in Kodak developer D-19, and is fixed, washed and dried. The image spread at the different exposures is shown in Table I below.

EXAMPLE 3 TABLE I Image size, it

Element 1X exposure exposure Example:

In photographing images of grossly different intensities and which are in close proximity in the image plane, the over-exposed image in the elements of Examples 2 and 3 spreads so much that the image of lesser intensity is obscured. However, the element of Example 1, which illustrates the invention, drastically reduces image spread.

The unobviousness of the present invention will be further illustrated by Examples 4-8. In these examples, five elements are prepared. The element of Example 5 is the same as that of Example 1 and illustrates this invention. The other examples show the results obtained when one or more of the layers of the invention are modified or deleted.

EXAMPLE 4 A photographic element is prepared exactly the same as that in Example 1 except that it contains no antihalation layer.

EXAMPLE 5 A photographic element is prepared exactly the same as the element described in Example 1.

EXAMPLE 6 A photographic element is prepared exactly the same as in Example 1 except that the dyes are deleted from the antihalation layer. The element of this example, therefore, consists of an undyed gelatin layer in place of the gelatin layer containing antihalation dyes used in the element of Example 1.

EXAMPLE 7 A photographic element is prepared exactly as in Example 1 except that the first emulsion layer (i.e., the non-image recording emulsion layer) is omitted.

EXAMPLE 8 A photographic element is prepared exactly the same as in Example 1 except that it contains no first emulsion layer (i.e., the non-image recording emulsion layer) and no antihalation layer. In other words, it consists only of an image recording layer on a cellulose acetate support, which is laminated to glass.

Samples of each of the photographic elements prepared as described in Examples 4-8 have a small circular images 240 microns in diameter contact printed thereon with separate samples of each coating receiving exposures of 1 second, 2 seconds, 4 seconds, seconds and 60 seconds. The 1 second exposure is much greater than that required to produce maximum density. The exposed elements are developed by the procedure of Example 1. The resulting image sizes are measured and are given in Table II. The difference in the size of the images shows the relative reductions in image spread. It wil be seen from this table that the image spread in the element of Example 5, which illustrates the invention, is drastically less than the image speed in the elements of Examples 4, 6, 7 and 8 which are shown herein for comparison purposes.

TABLE II Image size in microns at exposures of Element 1 see. 2 see. 4 see. 10 sec. 60 see.

Example:

EXAMPLE 9 A photographic element is prepared exactly as in Example 1 except that no magenta forming coupler is present, and the image forming emulsion is about ten times as slow as the image forming emulsion used in the above examples. It is coated at a concentration of 190 mg. silver per square foot instead of 150 mg. silver per square foot, and has a thickness of approximately 2 microns. It is exposed exactly as described in Examples 4-8 above. After exposure, it is developed at room temperature for 4 minutes in Kodak developer D19, and is fixed, washed and dried. It is compared with a control which is made in exactly the same manner, except that the control has no first non-image forming emulsion layer. In other words, the control consists of a support having thereon an antihalation layer, and thereover the image recording layer. The control is exposed and processed in exactly the same manner. The size of the images obtained in the control layer.

and sample elements are measured. A substantial reduction in image size is obtained with this example, as shown in Table III below.

TABLE III Image size in ,u at exposures of- Element 1 sec. 2 sec. 4 see. 10 see. 60 sec. nest @1713133311: 333 353 333 533 133 EXAMPLE 10 A photographic element is prepared exactly as described in Example 1 except that there is added to the first emulsion layer 300 mg. per mole of silver of anhydro'4,5,4,5'- dibenzo-9-ethyl 3,3 bis-('y-sulfopropyl)-thiacarbocyanine hydroxide and 200 mg. per mole of silver of anhydro-3ethyl-9-methyl-3'-(4-sulfobutyl thiacarbocyanine hydroxide; and, the emulsion employed in the image recording layer is spectrally sensitized. This sample is compared to a control prepared in exactly the same manner except that the absorbing dyes are omitted from the first emulsion layer. The sample and the control are then exposed to white light spot exposures 240 microns in diameter, the exposures being sufiicient to give maximum density. After exposure, the sample and the control are processed exactly as described in Example 1. The image spread of the sample containing the absorbing dyes and the first emulsion layer is 50% less than that of the control which does not contain any absorbing dyes in first emulsion The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be effected Within the spirit and scope of the invention described hereinabove and in the appended claims.

I claim:

1. A photographic element comprising a support having coated on one side thereof, in the order given:

(1) an antihalation layer;

(2) a hydrophilic colloid layer of from 10 to 40 microns in thickness and having dispersed therein silver halide grains having an average diameter of from .1 to 1 micron; and, t

(3) an image recording layer comprising a light sensitive silver halide emulsion layer of from 1 to 10 microns in thickness, the silver halide grains of said emulsion layer having an average grain size diameter of from 1 to 4 microns, said silver halide grains being coarser than the silver halide grains in said hydrophilic colloid layer.

2. A photographic element as defined in claim 1 wherein said hydrophilic colloid layer contains filter material which absorbs radiation longer than about 500 nm., and said image recording layer is sensitive to radiation longer than about 500 nm.

3. A photographic element which exhibits low image spread comprising a support having coated on one side thereof, in the order given:

(1) an antihalation layer;

(2) a hydrophilic colloid layer from 10 to 40 microns in thickness containing silver halide grains having an average diameter of from .1 to 1 micron; and,

(3) an image recording layer comprising a hydrophilic colloid layer of from 1 to 10 microns in thickness and having dispersed therein light sensitive silver halide grains having an average diameter of 1 to 4 microns, together with a photographic color former, said silver halide grains being coarser than the silver halide grains in said hydrophilic colloid layer.

4. A photographic element as defined in claim 3 wherein said hydrophilic colloid is gelatin.

5. A photographic element as defined in claim 3 wherein said hydrophilic colloid layer containing silver halide grains having an average diameter of from .1 to 1 micron contains filter material which absorbs red and green radiation; and, the silver halide grains in said image recording layer are panchromatically sensitized.

6. A photographic element comprising a glass support having the following layers coated thereon, in the order given:

( 1) an antihalation layer comprising gelatin containing a bleachable dye;

(2) a first layer about 10 to 12 microns thick comprising photographic silver bromoiodide grains dispersed in gelatin, said grains having an average size of approximately 0.25 micron; and,

(3) an image recording layer about 4 microns thick comprising photographic light-sensitive silver bromoiodide grains dispersed in gelatin, said grains having an average size of from about 2.0 to about 2.5 microns, and said emulsion containing a pyrazolone photographic color former.

7. A photographic element as defined in claim 6 wherein said first layer comprises filter dyes which absorb red and green radiation; and, the silver halide grains in said image recording layer are panchromatically sensitized.

8. The method of making photo-graphic images having a minimum amount of spread which comprises exposing a photographic element comprising a support having coated on one side thereof, in the order given:

(1) an antihalation layer;

8 (2) a hydrophilic colloid layer of from 10 to microns in thickness and having dispersed therein silver halide grains having an average diameter of from .1 to 1 micron; and,

(3) an image recording layer comprising a light sensitive silver halide emulsion layer of from 1 to 10 microns in thickness, the silver halide grains of said emulsion layer having an average grain size of from 1 to 4 microns, said image recording layer containing a photographic color former, and said silver halide grains being coarser than the silver halide grains in said hydrophilic colloid layer; developing said element with a primary aromatic amino color developing agent to form dye by the reaction of said photographic color former with oxidized color developing agent, and removing silver image and undeveloped silver halide from said element.

9. The method of making photographic images as defined in claim 8 wherein said hydrophilic colloid layer contains filter material which absorbs radiation longer than about 500 nm., and said image recording layer is sensitive to radiation longer than about 500 nm.

References Cited UNITED STATES PATENTS 3,140,179 7/1964 Russell 9668 3,353,957 11/1967 Blake 9668 3,402,046 9/1968 Zwick 9674 3,413,122 11/1968 Blake 9668 NORMAN G. TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner US. Cl. X.R. 

